Food product trays typically have planar or flat, symmetric seal flanges. Traditional sealing methods utilise a sealing surface that is applied in one plane that is immediately above the planar surface of the seal flanges. In addition, such methods typically utilize an equal length of lid film stock for a given length of the seal flange of the container such that the seal flange length is equal to its projected dimension on the original, unformed sheet.
The above described methods would not be effective to seal packages having flanges that do not lie in one plane, such as curved or non-planar flanges. For example, in a package with one or more curved flanges, the traditional methods of measuring and applying the lid film would not be feasible because the projected dimension of the seal flange would be less than the length along the curve of the sealing flange and a greater length of lid material would be needed for a corresponding length of the base package. In a package where a portion of the flange curves or otherwise deviates out of the flat plane, traditional methods would result in the curved flange remaining unsealed because the sealing surface would only applied in one plane and would not contact the curved portion of the seal flange.
A method of sealing a package containing a food product is provided. The method comprises applying a lid to a non-planar flange surrounding a periphery of the food package. The method comprises supporting at least a portion of the non-planar flange and progressively sealing the lid to the supported portion of the non-planar flange by applying pressure at one or more tangent points against the lid and the flange using a sealing member having a pressure applying surface that rotates about an axis of rotation and one of radially varies relative to the axis of rotation and the axis of rotation reciprocates.
The step of supporting at least a portion of the non-planar flange can further include supporting the flange along its entire surface during the step of progressively sealing the lid.
The step of supporting at least a portion of the non-linear flange can further include supporting the flange using a flange support surface that rotates about an axis of rotation. The axis of rotation of the flange support surface can be parallel to the axis of rotation of the pressure applying surface.
The non-planar flange can advance in a linear direction perpendicular to the axis of rotation of the pressure applying surface.
The non-planar flange can have a projected length in a machine direction of less than a length along she flange in the machine direction.
The method can further a step of tacking a portion of the lid to a leading end of the non-planar flange.
The method can include sealing a portion of the lid to a leading end of the flange in a first plane and sealing another portion of the lid to a trailing end of the flange in a second plane.
The method of can further include a step of transporting the package along a conveyor surface with a portion of the lid attached to the non-planar flange and a portion of the lid unattached to the non-planar flange.
The method can further include providing a plurality of at least one seat including a cavity configured to receive the package with the flange being at least in part outside of the cavity.
The method can further include a step of providing at least one cylindrical top sealing member having at least one sealing surface configured to rotate and contact the non-planar flange to seal the lid to the package.
The method can also include providing two cylindrical top sealing members where one of the sealing members seals one portion of the lid to one portion of the non-planar flange and the other of the sealing members seals another portion of the lid to another portion of the non-planar flange. The method can further include rotating the two cylindrical sealing members at different speeds.
The method can also include a step of providing a bottom rotary die having a plurality of seats, each seat having a plurality of support surfaces configured to support the non-planar flange, and a top rotary sealing member having a plurality of sealing surfaces configured to rotate and contact the support surfaces of the seats to seal the lid to the package.
The method can also include a step of providing a conveyor surface including a plurality of seats, each seat having a plurality of support surfaces configured to support the non-planar flange, and a top rotary sealing member having a plurality of sealing surfaces configured to rotate over and contact each of the support surfaces to seal the lid to the package.
The method can further include applying the lid onto the flange using a pick and place device including a vacuum.
The method can further include a step of providing the sealing member having the sealing surface that is entirely non-planar.
The method can further include a step of applying the lid onto the flange from a supply film roll using a plurality of rollers, at least one of the rollers including a cutting surface.
The method can further include placing and sealing the lid onto the non-planar flange at one station.
The method can further include creating a pressure atmosphere in the package that urges the lid in a direction away from the food product stored in the package.
The method can also include creating a protective atmosphere in the food package to increase a shell life of the food product stored in the package.
The lid can be made of a flexible film or can be made of a rigid material, such as a suitably rigid blow-molded, injection molded or thermoformed plastic.
The method can further comprise providing a food storage package having a non-planar flange. The package can have a top surface that is entirely non-planar. The package can alternatively have a bottom surface that is in part planar and in part non-planar. The package can include a tray having a non-planar flange.
The method can include a step of using the sealing member having a sealing surface that radially varies relative to the axis of rotation.
The method can include a step of using the sealing member having an axis of rotation that reciprocates.
A package including a non-planar flange made according to any one of aforementioned methods is also provided. The package can include a tray having a non-planar flange.
An apparatus for sealing a lid to a non-planar flange surrounding a periphery of a package containing a food product is provided. The apparatus includes a conveyor surface configured to advance the package. The apparatus further includes a bottom rotary die protruding at least in part above the conveyor surface and having a plurality of seats, each seat having a plurality of support surfaces configured to support at least a portion of the non-planar flange. The apparatus also includes at least one top sealing member having at least one sealing surface configured to rotate and contact the non-planar flange to seal the lid to the flange.
The at least one top sealing member can rotate about a reciprocating axis of rotation to seal the lid to an entire surface of the flange.
The at least one top sealing member can comprise two top sealing members each configured to rotate about a reciprocating axis of rotation to seal the lid to the flange.
The at least one top sealing member can include a first top sealing member configured to seal one portion of the lid to one portion of the flange and a second top sealing member configured to seal another portion of the lid to another portion of the flange.
The top sealing member can comprise a plurality of sealing surfaces and is configured to rotate about one axis of rotation and contact each of the support surfaces of the seats to seal the lid to the package.
Another apparatus for sealing a lid to a non-planar flange surrounding a periphery of a package containing a food product is also provided. The apparatus comprises a conveyor configured to advance the package. The conveyor includes a plurality of seats formed thereon having a plurality of support surfaces configured to support the non-planar flange. The apparatus further includes at least one top sealing member having at least one sealing surface configured to rotate and press the lid against the flange.
The top sealing member can comprise a plurality of sealing surfaces and is configured to rotate about one axis of rotation and contact each of the support surfaces of the seats to seal the lid to the package.
The at least one sealing surface can be non-planar. The at least one sealing surface can be made of a resilient material.
The apparatus can further comprise a device configured to transfer the lid from a supply source and apply the lid onto the flange of the package. The device can comprise a vacuum source configured to lift and move the package.